C API¶
The GSD C API consists of a single header and source file. Developers can drop the implementation into any package that needs it.
Functions¶
-
int
gsd_create
(const char *fname, const char *application, const char *schema, uint32_t schema_version)¶ Create an empty gsd file with the given name. Overwrite any existing file at that location. The generated gsd file is not opened. Call
gsd_open()
to open it for writing.- Parameters
fname – File name.
application – Generating application name (truncated to 63 chars).
schema – Schema name for data to be written in this GSD file (truncated to 63 chars).
schema_version – Version of the scheme data to be written (make with
gsd_make_version()
).
- Returns
GSD_SUCCESS (0) on success. Negative value on failure:
GSD_ERROR_IO: IO error (check errno).
-
int
gsd_create_and_open
(struct gsd_handle* handle, const char *fname, const char *application, const char *schema, uint32_t schema_version, gsd_open_flag flags, int exclusive_create)¶ Create an empty gsd file with the given name. Overwrite any existing file at that location. Open the generated gsd file in handle.
- Parameters
handle – Handle to open.
fname – File name.
application – Generating application name (truncated to 63 chars).
schema – Schema name for data to be written in this GSD file (truncated to 63 chars).
schema_version – Version of the scheme data to be written (make with
gsd_make_version()
).flags – Either
GSD_OPEN_READWRITE
, orGSD_OPEN_APPEND
.exclusive_create – Set to non-zero to force exclusive creation of the file.
- Returns
GSD_SUCCESS (0) on success. Negative value on failure:
GSD_ERROR_IO: IO error (check errno).
GSD_ERROR_NOT_A_GSD_FILE: Not a GSD file.
GSD_ERROR_INVALID_GSD_FILE_VERSION: Invalid GSD file version.
GSD_ERROR_FILE_CORRUPT: Corrupt file.
GSD_ERROR_MEMORY_ALLOCATION_FAILED: Unable to allocate memory.
-
int
gsd_open
(struct gsd_handle* handle, const char *fname, gsd_open_flag flags)¶ Open a GSD file and populates the handle for use by later API calls.
- Parameters
handle – Handle to open.
fname – File name to open.
flags – Either
GSD_OPEN_READWRITE
,GSD_OPEN_READONLY
, orGSD_OPEN_APPEND
.
- Returns
GSD_SUCCESS (0) on success. Negative value on failure:
GSD_ERROR_IO: IO error (check errno).
GSD_ERROR_NOT_A_GSD_FILE: Not a GSD file.
GSD_ERROR_INVALID_GSD_FILE_VERSION: Invalid GSD file version.
GSD_ERROR_FILE_CORRUPT: Corrupt file.
GSD_ERROR_MEMORY_ALLOCATION_FAILED: Unable to allocate memory.
-
int
gsd_truncate
(gsd_handle* handle)¶ Truncate a GSD file.
After truncating, a file will have no frames and no data chunks. The file size will be that of a newly created gsd file. The application, schema, and schema version metadata will be kept. Truncate does not close and reopen the file, so it is suitable for writing restart files on Lustre file systems without any metadata access.
- Parameters
handle – Open GSD file to truncate.
- Returns
GSD_SUCCESS (0) on success. Negative value on failure:
GSD_ERROR_IO: IO error (check errno).
GSD_ERROR_NOT_A_GSD_FILE: Not a GSD file.
GSD_ERROR_INVALID_GSD_FILE_VERSION: Invalid GSD file version.
GSD_ERROR_FILE_CORRUPT: Corrupt file.
GSD_ERROR_MEMORY_ALLOCATION_FAILED: Unable to allocate memory.
-
int
gsd_close
(gsd_handle* handle)¶ Close a GSD file.
- Parameters
handle – GSD file to close.
Warning
Ensure that all
gsd_write_chunk()
calls are committed withgsd_end_frame()
before closing the file.- Returns
GSD_SUCCESS (0) on success. Negative value on failure:
GSD_ERROR_IO: IO error (check errno).
GSD_ERROR_INVALID_ARGUMENT: handle is NULL.
-
int
gsd_end_frame
(gsd_handle* handle)¶ Commit the current frame and increment the frame counter.
- Parameters
handle – Handle to an open GSD file.
- Returns
GSD_SUCCESS (0) on success. Negative value on failure:
GSD_ERROR_IO: IO error (check errno).
GSD_ERROR_INVALID_ARGUMENT: handle is NULL.
GSD_ERROR_FILE_MUST_BE_WRITABLE: The file was opened read-only.
GSD_ERROR_MEMORY_ALLOCATION_FAILED: Unable to allocate memory.
-
int
gsd_write_chunk
(struct gsd_handle* handle, const char *name, gsd_type type, uint64_t N, uint32_t M, uint8_t flags, const void *data)¶ Write a data chunk to the current frame. The chunk name must be unique within each frame. The given data chunk is written to the end of the file and its location is updated in the in-memory index. The data pointer must be allocated and contain at least contains at least
N * M * gsd_sizeof_type(type)
bytes.- Parameters
handle – Handle to an open GSD file.
name – Name of the data chunk.
type – type ID that identifies the type of data in data.
N – Number of rows in the data.
M – Number of columns in the data.
flags – Unused, set to 0.
data – Data buffer.
Note
If the GSD file is version 1.0, the chunk name is truncated to 63 bytes. GSD version 2.0 files support arbitrarily long names.
- Returns
GSD_SUCCESS (0) on success. Negative value on failure:
GSD_ERROR_IO: IO error (check errno).
GSD_ERROR_INVALID_ARGUMENT: handle is NULL, N == 0, M == 0, type is invalid, or flags != 0.
GSD_ERROR_FILE_MUST_BE_WRITABLE: The file was opened read*only.
GSD_ERROR_NAMELIST_FULL: The file cannot store any additional unique chunk names.
GSD_ERROR_MEMORY_ALLOCATION_FAILED: failed to allocate memory.
-
const struct gsd_index_entry_t*
gsd_find_chunk
(struct gsd_handle* handle, uint64_t frame, const char *name)¶ Find a chunk in the GSD file. The found entry contains size and type metadata and can be passed to
gsd_read_chunk()
to read the data.- Parameters
handle – Handle to an open GSD file.
frame – Frame to look for chunk.
name – Name of the chunk to find.
- Returns
A pointer to the found chunk, or NULL if not found.
-
int
gsd_read_chunk
(gsd_handle* handle, void* data, const gsd_index_entry_t* chunk)¶ Read a chunk from the GSD file. The index entry must first be found by
gsd_find_chunk()
.data
must point to an allocated buffer with at leastN * M * gsd_sizeof_type(type)
bytes.- Parameters
handle – Handle to an open GSD file.
data – Data buffer to read into.
chunk – Chunk to read.
- Returns
0 on success
GSD_SUCCESS (0) on success. Negative value on failure:
GSD_ERROR_IO: IO error (check errno).
GSD_ERROR_INVALID_ARGUMENT: handle is NULL, data is NULL, or chunk is NULL.
GSD_ERROR_FILE_MUST_BE_READABLE: The file was opened in append mode.
GSD_ERROR_FILE_CORRUPT: The GSD file is corrupt.
-
uint64_t
gsd_get_nframes
(gsd_handle* handle)¶ Get the number of frames in the GSD file.
- Parameters
handle – Handle to an open GSD file.
- Returns
The number of frames in the file, or 0 on error.
-
size_t
gsd_sizeof_type
(gsd_type type)¶ Query size of a GSD type ID.
- Parameters
type – Type ID to query
- Returns
Size of the given type, or 0 for an unknown type ID.
-
uint32_t
gsd_make_version
(unsigned int major, unsigned int minor)¶ Specify a version number.
- Parameters
major – major version.
minor – minor version.
- Returns
a packed version number aaaa.bbbb suitable for storing in a gsd file version entry.
-
const char *
gsd_find_matching_chunk_name
(struct gsd_handle* handle, const char* match, const char *prev)¶ Search for chunk names in a gsd file.
- Parameters
handle – Handle to an open GSD file.
match – String to match.
prev – Search starting point.
To find the first matching chunk name, pass
NULL
forprev
. Pass in the previous found string to find the next after that, and so on. Chunk names match if they begin with the string inmatch
. Chunk names returned by this function may be present in at least one frame.- Returns
Pointer to a string,
NULL
if no more matching chunks are found found, orNULL
ifprev
is invalid.
-
int
gsd_upgrade
(gsd_handle* handle)¶ Upgrade a GSD file to the latest specification.
- Parameters
handle – Handle to an open GSD file.
- Returns
0 on success
GSD_SUCCESS (0) on success. Negative value on failure:
GSD_ERROR_IO: IO error (check errno).
GSD_ERROR_INVALID_ARGUMENT: handle is NULL, data is NULL, or chunk is NULL.
GSD_ERROR_FILE_MUST_BE_WRITEABLE: The file was opened in the read only mode.
Constants¶
Data types¶
Open flags¶
-
gsd_open_flag
GSD_OPEN_READWRITE
¶ Open file in read/write mode.
-
gsd_open_flag
GSD_OPEN_READONLY
¶ Open file in read only mode.
-
gsd_open_flag
GSD_OPEN_APPEND
¶ Open file in append only mode.
Data structures¶
-
gsd_handle
¶ Handle to an open GSD file. All members are read-only. Only public members are documented here.
-
gsd_header_t
header
¶ File header. Use this field to access the header of the GSD file.
-
gsd_open_flag
open_flags
¶ Flags used to open the file.
-
gsd_header_t
-
gsd_header_t
¶ GSD file header. Access version, application, and schema information.
-
uint32_t
gsd_version
¶ GSD file format version from
gsd_make_version()
-
char application[64]
Name of the application that generated this file.
-
char schema[64]
Name of data schema.
-
uint32_t
schema_version
¶ Schema version from
gsd_make_version()
.
-
uint32_t
-
gsd_index_entry_t
¶ Entry for a single data chunk in the GSD file.
-
uint8_t
type
¶ Data type of the chunk. See Data types.
-
uint8_t
-
gsd_open_flag
¶ Enum defining the file open flag. Valid values are
GSD_OPEN_READWRITE
,GSD_OPEN_READONLY
, andGSD_OPEN_APPEND
.
-
gsd_type
¶ Enum defining the file type of the GSD data chunk.
-
gsd_error
¶ Enum defining the possible error return values.
-
uint8_t
¶ 8-bit unsigned integer (defined by C compiler).
-
uint32_t
¶ 32-bit unsigned integer (defined by C compiler).
-
uint64_t
¶ 64-bit unsigned integer (defined by C compiler).
-
int64_t
¶ 64-bit signed integer (defined by C compiler).